Making single-ended amplifiers with 6L6 bile duct, 6L6 Power Amplifier
Keywords: 6L6 electronic pipe power discharge circuit diagram
Author: Zhong Wenxiang
First, the optocoupler of the photocouplex is used in the optical coupling device of a photocryreo, which is mostly 20% to 300% (such as 4 N35), while PC817 (not recommended) is 80% to 160%, Darlington type. Optocouplers (such as 4 N30) can reach 100% to 5000%. This indicates that the same output current is to be obtained, and the latter only needs a small input current. Therefore, the CTR parameter is similar to the HFF of the transistor. The linear optical coupler is typically shown by the normal optical coupler, respectively, shown by the dashed line and solid line in the figure below.
It can be seen from the following figure. The CTR-IF characteristic curve of the ordinary optocoupler is non-linear, and the nonlinear distortion of TF hours is particularly severe, so it is not suitable for transmission analog signals. The CTR-IF characteristic curve of the linear optical coupler has good linearity, especially when transmitting small signals. Its AC current transmission ratio (△ CTR = Δ IC / ΔIF) is very close to the DC current transmission ratio Ctr value. Therefore, it is suitable for transmitting an analog voltage or current signal that enables a linear relationship between the output and input. This is an important feature. Using the photocoupler is mainly to provide isolation for the input circuit and the output circuit. When the design circuit, the selected photocoupler must conform to the standard of internal and international isolation, from the UK Esoum (ISOCOM) The company, the 4N ×× series (eg, 4N25, 4N26, 4I35) optocouplers produced by Motorola, USA, currently in domestic applications. There are two main coupling components that must have a higher coupling factor. There are two main coupling factors. There are two main coupling, and there are two main signal isolation, and the signal quality is improved by eliminating loop current, blocking noise signal, and common mode transient. The second is electrical insulation, preventing the photocoupler and the sensitive circuit indi high voltage potential to cause damage, and users can safely use components or unpredictable. When switching power supply isolation and designing a photocoupless feedback switch supply or isolation transmission analog signal, the model number and parameters of the linear optical coupler must be correctly selected. In addition to the necessary principles must be followed, the following principles must be followed: (1 Recommended linear optocoupler, characterized by a CTR value to do linear adjustments within a certain range. (2) The allowable range of the current transmission ratio (CTR) of the optocoupler is 50% to 200%. This is because when CTR<50%, the LED in the optocoupler requires a large working current (IF>5.0mA) ), In order to control the duty cycle normally, this increases the power consumption of optocoupler. If CTR>200%. When the startup circuit or when the load has a mutation, it is possible to malfunction, affecting the normal output. (3) If an amplifier circuit is driven to drive the photocoupleer, it must be carefully designed to ensure that it can compensate for the temperature unstable and drift of the coupler. The photocoupler used above operates in linear mode, and the control voltage is added to the input end of the photocoupler, and a voltage for further controlling the next level circuit is proportionally generated.
Second, the production of optical isolation of the 6L6 single-ended amplifier is a very common signal isolation form. Since the optocouple circuit is simple, it is often used in a digital isolation circuit or a data transmission circuit. For AC analog signals, ordinary optocoupler is poor because the linearity of the input and output is poor, and it is limited to the AC analog signal isolation. Application of towel. A relatively good choice for AC analog signals is to use linear optocouplers. The development of large-capacity and high speed optocouplers is currently in advance, and due to the linearity and temperature change of the optocoupler input and output, the effect is large in the audio system, for pre-stage and small signals for isolation coupling. It is more appropriate, but it is also used for a large current isolation drive amplifier composed of Darlington composite tube. Its highlighting advantage is to use optocoupler oriented transmission, prevent output signals from generating "inverted" in front stage. , Make the playback music have a good shape frame, sound quality, natural and smooth! The circuit schematic diagram of the electronic pipe 6L6 single-end power amplifier with a photoelectric isolation system is suitable for computer sound card audio output, and a number of magical audio signals such as a laser player. Has isolated noise, anti-interference, etc., high signal-to-noise is relatively high. The circuit spectrum isolation system and the power amplifier are both, and the photoelectric isolation system is composed of photoelectric combiner 4N35 and the sealing element. The photocoupler is filled with arsenide (GaAs) light emitting diode (LED) and the photosensitive tube in the same tube shell. The internal composition. The transmission ratio of the photocoupler is about 100%, and the transmission rate is about 4 μs. The input signal is converted into a optical signal via a light-emitting diode. After the photomic tube receives the electrical signal, the electrical signal is directly acting on the 6SN7 cathode, and the 6SN7 grid circuit is low noise output, and the lower level is used as voltage and power amplification push speaker. The photoelectric isolation part of the operating current adjustment method is as follows, the pre-stage operating voltage is 5 ~ 15V, taken from the signal source power supply, the current flow resistance is appropriately adjusted according to the working current, the positive pressure drop of the luminous pipe is about L3V, and the working current is generally taken 5 ~ 10mA, the working voltage VCE of the photosensitive triode takes 8 to 10V, and the current is about 2-3 mA.
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